Prolactin (PRL) has been reported to have many biological actions. However, recent studies indicate that PRL really is a family of hormones, each PRL variant having different biological activities. The aim of the studies proposed in this application is to re-evaluate the role of PRL in various physiological processes based on the relative amounts of the PRL variants present. Since recent work has shown that the glycosylation of PRL alters its biological activity, determination of the factors that affect synthesis and secretion of the glycosylated form may provide insight into the physiological role of glycosylated PRL. The studies proposed will focus on the differences in the secretory patterns of the glycosylated form of human PRL (G-hPRL) in comparison to those of the nonglycosylated form of human PRL (hPRL). The specific aims are: 1) To measure G-hPRL and hPRL in normal women, hormoprolactinemic women with galactorrhea and amenorrhea, and hyperprolactinemic women. 2) To use primary cultures of human pituitary cells as a model system to investigate the effects of various secretagogues on the in vitro synthesis and release of G-hPRL and hPRL. 3) To develop monoclonal antibodies that will be specific for G-hPRL or hPRL and to use these monoclonal antibodies to develop specific immunoassays. 4) To study individual pituitary cells in vitro to determine if they contain and are capable of secreting both G-hPRL and hPRL. The hypothesis to be tested is that a specific PRL variant performs a specific physiological function. This hypothesis implies that this difference in function will be reflected in the differential secretion patterns of G-hPRL and hPRL.